[mythtv-users] Can I play scaled HDTV content on a standard TV?

Brad Templeton brad+myth at templetons.com
Thu Dec 9 00:20:11 UTC 2004

On Wed, Dec 08, 2004 at 05:06:19PM -0600, Lane Schwartz wrote:
> On #5, yes, I meant the cpu cost of playback only. 
> As I said, I'm really pleased to hear these answers. I plan to get a
> pcHDTV card before Big Brother comes along in July, but I don't plan
> to get an HDTV that soon. I'm hopeful that my processor will be able
> to handle HD playback, as that was the entire reason why I went with a
> high-powered P4.

You may not be aware that in the digital TV spectrum, it is common that
the local HD stations include a sub channel which is the same but in
standard definition -- though it is pan and scan, not widescreen or

So with your pcHDTV, you can just record, if you wish, the digital TV
image and not have to scale it down or transcode it.

Of course, if widescreen was your goal you must record the full one.
While in theory they could transmit widescreen EDTV, this is not so

In this area, the NBC, FOX, WB, UPN and I think CBS stations do this.
ABC transmits their news channel on their 2nd channel.  PBS digital is
an interesting 5 channel layout.  During the day, the HD channel is blank
and 4 SD channels are shown.  At night it's one HD channel and one SD
channel, but not a mirror of the HD channel.

One thing I have found annoying is that the TV stations always broadcast
at exactly the same resolution.  Ie. the NBC channel is always in 1080i,
even when showing something in standard definition.   They don't swtich
down to 480p.

What this means is when a standard def show is on, if you record it, you
will waste a lot of disk space.  While it does compress a bit better than
a full signal, Sunday's half-hour Malcom in the Middle (normally a 720p
show) was a standard def one, and took 2.9 gb for half an hour!

Worse, they put the little ad at the front saying "In widescreen HDTV
where available" when it wasn't.

Of corurse they hate use recorders so what do they care.

Thus to manage things right, you must identify if the program you will
record is in HD, and try to record it from an SD channel, or somehow
arrange to transcode it.

Myth's transcoding is not yet hdtv aware, in that it doesn't realize you
have different transcoding goals for an mpeg2 tuned from a wintv-pvr than
you do for an HD recording.

More information about the mythtv-users mailing list